Abolishing the council tax and replacing it with local income tax (LIT) was a central plank of the SNP's election manifesto last May. Its popular appeal was fairness: council services would be funded by levying an extra 3p on the standard rate of income tax and therefore based on an ability to pay. One year on there is considerable confusion about whether it could be implemented as well as how it would work. It is not surprising, therefore, that the latest opinion poll conducted by System Three shows that almost one-third of Scots don't know whether they support or oppose a local income tax.

Among those who have a definite opinion, the supporters of LIT outnumber by two to one those who oppose it outright. However, with the supporters (46%) amounting to fewer than half the respondents, the figures belie the SNP's claim that the LIT policy is hugely popular.

The "don't knows" amount to a significant proportion across every age group, social class and party allegiance. The widest variations are geographical. In central Scotland, for example, there are more "don't knows" (44%) than supporters or opponents. That is a very clear indication that a sizeable section of the electorate want more detail about how LIT will affect them both as contributors and beneficiaries before deciding whether or not to support it.

The one area where more people oppose than support LIT is the north-east of Scotland. This perhaps indicates a distrust of local government financial management owing to Aberdeen City Council's precarious financial position which will be examined at a special hearing by the Accounts Commission next week.

There are many questions to be answered, such as how a tax which is not imposed on the wealthiest individuals living on investment income but will disadvantage families with two working parents will be fairer than council tax. However, the debate about the pros and cons of LIT has been subsumed in the political point-scoring between the SNP and the Labour government at Westminster over whether the proposal can be implemented at all. One issue is whether HM Revenue and Customs can collect an extra 3p on the standard rate of income tax, since it is prohibited from collecting local taxes. The other is the £400m gap that would appear in the funding if council tax benefits were witheld inder LIT. The SNP says it must continue to be paid and Labour argues that it is part of the council tax system and must disappear if it does.

Both issues have been used to bolster the SNP argument that Gordon Brown's government at Westminster is deliberately frustrating a policy supported by the majority of the Scottish people. On today's evidence, its best case is that the Scottish taxpayers might be inclined to favour LIT but remain to be convinced.